1. Field of the invention
This invention relates to a spread illuminating apparatus for signboards or various kinds of reflection type display apparatus.
2. Description of the Related Art
Nowadays, a function to display various information is added to electronic products, and it has become indispensable to install a display portion to display those information. Further, in a portable electronic product such as a portable telephone and a notebook personal computer, in which all components are expected to be miniaturized and light weighted, a liquid crystal display device which occupies a small area in the product and is light weighted has been widely used for the display portion (the ratio of thickness to the display area is quite small). However, since the liquid crystal display device itself does not emit light, in consideration of usage in a dark place or at night, a separate illuminating apparatus needs to be provided besides the liquid crystal display apparatus. In order to answer that demand, an illuminating apparatus as explained below has been invented.
In a spread illuminating apparatus, a transparent substrate made of a transparent material is disposed on a front surface or a back surface of a liquid crystal display device, a side surface of the transparent substrate is illuminated to introduce light into the transparent substrate, and the introduced light is supplied uniformly to the display portion of the liquid crystal device from the surface of the transparent substrate, thereby illuminating the entire liquid crystal display device.
As a light source to illuminate the side surface of the transparent substrate, a fluorescent tube (cold cathode ray fluorescent tube or hot cathode ray fluorescent tube) has been used conventionally. However, the fluorescent tube uses a high voltage to emit light requiring a means for supplying a high voltage, which is contrary to the desire that components of a portable product be miniaturized and light weighted. In order to solve such a problem, the present inventors have developed a spread illuminating apparatus using a light emitting diode, etc. as a spot-like light source, and the present applicant has disclosed a detail thereof in the Japanese patent application No. Hei 1-182076. A spread illuminating apparatus 1 having a light source which uses a light emitting diode comprises, as shown in FIGS. 7 and 8, a transparent substrate 2 and a light source 11 as main components, where a lower surface 5 of the transparent substrate 2 is disposed opposing an observing surface of a reflection type liquid crystal element. A difference from the conventional spread illuminating apparatus resides in that, instead of using a fluorescent tube as a bar-like light source, a spot-like light source 12 and a bar-like light conductive member 13 (in FIG. 8, it is indicated in black so that it can be easily distinguished) are provided as the light source 11.
In the example shown in the figure, a light emitting diode is used as a spot-like light source 12, and further, the light conductive member 13 made of a transparent material is disposed at a given spacing along one side surface 3 of the transparent substrate 2, and the spot-like light source 12 is disposed close to one end 14 of the light conductive member 13. Further, the light conductive member 13 is provided with an optical path conversion means 15. The optical path conversion means 15 is provided with, for instance, a triangular groove on a surface 19 opposite to a surface 18 opposing the one side surface 3 of the transparent substrate 2, thereby introducing the light entering the light conductive member 13 into the transparent substrate 2.
In order to introduce the light highly efficiently into the transparent substrate 2, longitudinal surfaces of the light conductive member 13 except the surface opposing the transparent substrate 2 are covered with a light reflection member 16 (cover). Further, the efficiency can be greatly improved by covering at least a part where the optical path conversion means 15 is formed even when the light reflection member 16 can not cover the surrounding surfaces of the light conductive member 13 on account of a designing restriction such as avoiding an interference with other components. For reference, the light reflection member 16 is formed of a hard resin molding surfaced with a film vapored with a metal such as silver, a white film or a film coated with white paint, or an aluminum plate or a stainless steel plate provided with a mirror finished surface and worked by bending.
As mentioned above, the spread illuminating apparatus 1 is constituted by a combination of the transparent substrate 2, the spot-like light source 12, the light conductive member 13 and the optical path conversion means 16. In order for the spread illuminating apparatus 1 to give off a desired brightness, the above constituent parts needs to be mutually positioned as precisely as possible. Further, since the spread illuminating apparatus 1 is often used in portable type electronic products, if no countermeasures are taken, in particular, against changes in the positional relation of the constituent parts due to aging, it may suffer a deterioration in brightness. Also, it is indispensable that the above constituent parts can be positioned easily when they put together for assembling the spread illuminating apparatus.
The present invention has been made in light of the above problem, and the purpose thereof is to realize a secure positioning of the bar-like light source to the transparent substrate to carry out easy assembling of the spread illuminating apparatus and to secure a desired brightness of the spread illuminating apparatus without an influence from aging.
According to a first aspect of the present invention, in a side light type spread illuminating apparatus, in which a bar-like light source is disposed close to a side surface of a transparent substrate made of a transparent material, a positioning means for setting the bar-like light source to the transparent substrate is provided. According to the present invention, the positional relation between the transparent substrate and the bar-like light source is ensured by the above positioning means, to thereby secure a desired brightness of the spread illuminating apparatus.
According to a second aspect of the present invention, the positioning means is provided on a cover which covers the bar-like light source, whereby the cover and the positioning means are integrally formed at a time. Further, the positional relation between the transparent substrate, the bar-like light source and the cover is ensured, to thereby secure a desired brightness of the spread illuminating apparatus.
According to a third aspect of the present invention, the positioning means is provided on at least one longitudinal end of the cover. In the case where the positioning means is provided merely on one end of the cover, one end of the transparent substrate and one end of the bar-like light source are set to coincide with the one end of the cover based on the positioning means. In the case of providing the positioning means on both ends of the cover, the positions of the end of the transparent substrate and the end of the bar-like light source are determined by those two positioning means.
According to a fourth aspect of the present invention, the positioning means is provided at a position of the cover, which is lapped over the transparent substrate. Accordingly, the positioning between the cover and the transparent substrate is secured.
According to a fifth aspect of the present invention, the positioning means is formed with a claw raised from the end of the cover. Thus, the positional relation between the transparent substrate, the bar-like light source and the cover is guaranteed by this claw.
According to a sixth aspect of the present invention, the bar-like light source comprises a bar-like light conductive member and a spot-like light source disposed on at least one end of the light conductive member. According to this constitution, in the side light type spread illuminating apparatus formed with the bar-like light conductive member and the spot-like light source, the positional relation between the light source and the transparent substrate is guaranteed, thereby securing a desired brightness for the spread illuminating apparatus.
According to a seventh aspect of the present invention, the positioning means is provided at a position clear of an end of the light conductive member in order to prevent the positioning means from blocking light entering the bar-like light conductive member from the spot-like light source.